1. Field of the Invention
The present invention relates to air-conditioning apparatus and is specifically concerned with room ejection units of central air-conditioning systems.
The invention may be most advantageously employed for creating comfortable conditions in hospitals, residential and commercial buildings, as well as for maintaining a normal humidity in refrigerating chambers.
2. Description of the Prior Art
In improving existing and developing new air-conditioning systems numerous attempts have been made to stabilize the indoor air conditions with varying outdoor atmospheric conditions and to reduce at the same time the specific power consumption of air conditioners. Although a great many new designs of air conditioners have been developed over the last 10-15 years, the central air-conditioning systems are the most extensively used ones. They have undergone no radical changes during the last 20 years. This evidences that the above-stated problem remains as yet to be solved adequately enough.
In recent years, there have been observed two different trends in this field: developing an efficient self-contained room air conditioner on the one hand and improving the primary air conditioner and secondary room unit of a central air-conditioning system on the other. Equipping all the rooms in the building with efficient self-contained air conditioners was believed to enable adequately comfortable conditions to be created in all the rooms regardless of their location and of the extent of their being heated due to insolation. Every such self-contained air conditioner should include a complete set of all the means needed for treating air and maintaining desired temperature. Thus, a self-contained air conditioner (cf. USSR Inventor's Certificate No. 151,005 Int. Cl. 2 F 24 F 3/14) comprises a freon compressor, a condenser, an evaporator, a coarse air filter, a heat exchanger, an electric air heater, a humidifier, and a fan, all said units being accommodated in a common housing of the air conditioner. It is clear that to ensure maintaining the predetermined air conditions, with the outdoor conditions varying over a wide range, the power drives and electric units of a self-contained air conditioner must have a considerable power reserve. The advantage of self-contained air conditioners is that their use does not require an air ductwork inside the building. Nevertheless, the self-contained air conditioners have found no wide application for a number of reasons lying in their constructional features and low energy efficiency. Among other things, a complex construction of the self-contained air conditioner results in its relatively high cost and affects its reliability and durability. Installing self-contained air conditioners in every room of a multistorey building raises the total power consumption to such an extent which the existing standard electric wiring cannot provide. In addition, to provide for heat removal from the condenser to the outside, a self-contained air conditioner must be installed in a window aperture, which is not always convenient. Still another disadvantage of the self-contained air conditioners is their large overall dimensions.
Efforts aimed at improving primary air conditioners and room units of central air-conditioning systems have proved to be more promising in this respect. The room units feature a simple construction, occupy little space, and can be located in any convenient place. Moreover, the total amount of power consumed by all the central air-conditioning system units in the building in much less than that which is needed in case all the rooms in the same building are equipped with the self-contained air conditioners. Owing to these and other advantages, central air-conditioning systems have gained an extensive application. A room ejection unit of a central air-conditioning system (cf. "Bacho Induction Units" of the Bacho Ventilation Ltd., Sweden, 1974) comprises a housing whose side walls, bottom, and cover define a mixing chamber. The lower portion of the mixing chamber accommodates a primary air supply manifold. A side wall of the housing has an inlet port wherein a surface heat exchanger is mounted; the heat exchanger is a coil connected to the heat carrier supply system. Such a room unit of the central air-conditioning system is successfully employed both for cooling and heating of air in summer and winter respectively, ensuring a stable temperature in the room. It is to be noted, however, that operation of a system with the above-described room units involves some inconveniences associated with the instability of humidity, which is accounted for by the fact that air supplied from the primary air conditioner to the units in different rooms is of the same humidity. At the same time conditions vary from room to room, and hence the operating conditions of the room units are different. In addition, the conditions in one and the same room vary considerably over a day, and since the air humidity control is a centralized one, it is practically impossible to maintain the optimum humidity in every room.
An attempt has been made to improve the accuracy of controlling humidity in the room by humidification of recirculating air in the room unit (cf. USSR Inventor's Certificate No. 367,318, Int. Cl. 2 F 24 F 3/14). This ejection room unit of a central air-conditioning system comprises a housing whose side walls, bottom, and cover define a mixing chamber. The lower portion of the mixing chamber accommodates a primary air supply manifold having nozzles and communicating with the primary air-conditioner. A side wall of the housing has an inlet port wherein a heat exchanger is mounted. The cover of the housing has an outlet port. The distinctive feature of this unit consists in that it is provided with a humidifier located in the mixing chamber. The humidifier is a water supply pipe arranged in the primary air supply manifold and having branch pipes connected to the nozzles thereof. The heat exchanger is a coil connected to the heat carrier supply system. The primary air supply manifold has the form of a box with nozzles passing through the box top cover. Flowing out of the nozzles, the primary air ejects water from the branch pipes and atomizes it in the mixing chamber, thereby humidifying the recirculating-primary air mixture. This ejection room unit makes possible an individual humidity control in every room. However, practice has shown that this construction is not free from some disadvantages.
One of these disadvantages consists in that the water accumulates on the manifold cover during continuous running of the unit floods the nozzles, and upsets the normal functioning of the humidifier. The water gets ejected from the unit into the room, which prevents an accurate control of the humidity.
Another disadvantage lies in a destabilizing effect exerted on humidifier performance by the coil on which moisture condenses in summer, whereas in winter, when a heated-up heat carrier is fed to the heat exchanger, the relative humidity of air in the room declines due to water evaporation. In addition, the operation of this unit requires a great deal of apparatus and pipes for heating, cooling, and feeding the heat carrier, whose normal functioning requires considerable power.